The invention proceeds from an electromechanical steering actuator, in particular for steer-by-wire application in motor vehicles, with an electronic closed-loop/open-loop control system that generates steering signals for an electric servomotor, which acts via a gear unit on a steering control element. In particular the servomotor acts on a rack of a rack-and-pinion steering system. The closed-loop/open-loop control system comprising a process computer that delivers corrective signals to the servomotor via a drive unit.
Such a steering actuator is known, for example, from DE 195 40 956. In the known electromechanical steering actuator, the mechanical connection between the steering column and the rack of the rack-and-pinion steering system can be broken to permit steer-by-wire steering. In the event of a fault in the power-assisted or the automatic steering system, this additional system is shut down and the driver regains mechanical control over the wheels to be steered. The known steering actuators for an automatic steering mode are not completely fault-tolerant.
In a vehicle with a steer-by-wire system, where there is no longer a mechanical connection between the steering wheel and the gear unit, care must be taken to ensure that the steering actuator is fault-tolerant.